Claude Code MCP

Instructions

Implementation Reference

• src/server/tools.ts:63-78 (handler)

  MCP tool handler for readFile: calls the readFile utility, handles errors, and returns formatted text content.

  async ({ file_path, offset, limit }) => {
    try {
      const content = await readFile(file_path, offset, limit);
      return {
        content: [{ type: "text", text: content }]
      };
    } catch (error) {
      return {
        content: [{ 
          type: "text", 
          text: error instanceof Error ? error.message : String(error)
        }],
        isError: true
      };
    }
  }

• src/server/tools.ts:58-62 (schema)

  Input schema using Zod for readFile tool parameters: file_path (string), offset (number optional), limit (number optional).

  {
    file_path: z.string().describe("The absolute path to the file to read"),
    offset: z.number().optional().describe("The line number to start reading from"),
    limit: z.number().optional().describe("The number of lines to read")
  },

• src/server/tools.ts:55-79 (registration)

  Registers the readFile tool on the MCP server with name, description, input schema, and handler function.

  server.tool(
    "readFile",
    "Read a file from the local filesystem",
    {
      file_path: z.string().describe("The absolute path to the file to read"),
      offset: z.number().optional().describe("The line number to start reading from"),
      limit: z.number().optional().describe("The number of lines to read")
    },
    async ({ file_path, offset, limit }) => {
      try {
        const content = await readFile(file_path, offset, limit);
        return {
          content: [{ type: "text", text: content }]
        };
      } catch (error) {
        return {
          content: [{ 
            type: "text", 
            text: error instanceof Error ? error.message : String(error)
          }],
          isError: true
        };
      }
    }
  );

• src/utils/file.ts:15-34 (helper)

  Utility function implementing file reading logic with fs.promises.readFile, supporting line-based offset and limit.

  export async function readFile(
    filePath: string,
    offset?: number,
    limit?: number
  ): Promise<string> {
    try {
      let content = await fs.readFile(filePath, 'utf-8');
      
      if (offset || limit) {
        const lines = content.split('\n');
        const startLine = offset ? offset - 1 : 0;
        const endLine = limit ? startLine + limit : lines.length;
        content = lines.slice(startLine, endLine).join('\n');
      }
      
      return content;
    } catch (error) {
      throw error;
    }
  }